Acoustic flow sensor for continuous medication flow measurements and feedback control of infusion

ABSTRACT

An infusion system determines a volumetric flow rate of infusion fluid delivered by an infusion pump along a flow path based on: an upstream acoustic signal emitted by at least one upstream acoustic sensor and detected by at least one downstream acoustic sensor; a downstream acoustic signal emitted by the downstream acoustic signal and detected by the upstream acoustic sensor; and a phase delay between the upstream acoustic signal and the downstream acoustic signal either upstream or downstream. The infusion system automatically adjusts the infusion pump based on the determined volumetric flow rate to achieve a desired volumetric flow rate of the infusion fluid along the flow path.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No.62/348,301, filed Jun. 10, 2016, entitled ACOUSTIC FLOW SENSOR FORCONTINUOUS MEDICATION FLOW MEASUREMENTS AND FEEDBACK CONTROL OFINFUSION. The contents of the aforementioned application are herebyincorporated by reference in its entirety as if fully set forth herein.The benefit to the foregoing application is claimed under theappropriate legal bias, including, without limitation, under 35. U.S.C.§ 119(e).

BACKGROUND OF THE INVENTION Field of the Invention

The disclosure relates to flow detection systems and methods foroperating an infusion pump which utilize a high-frequency acoustic,closed loop system to measure and control the volumetric flow rate ofthe infusion pump.

Background of the Invention

Infusion systems and methods often operate in an open loopconfiguration, without receiving feedback regarding the volume of fluidbeing delivered to the patient. These infusion systems and methodstypically rely on tightly controlled tolerances to fabricate theindividual components and assemblies of the infusion pumping system tomaintain the accuracy of delivered medication over a prescribed time.The accuracy of the amount of the prescribed medication being deliveredto the patient by current infusion systems and methods can vary overtime due to the component degradation over the life of the infuser.Additionally, requirements for tight tolerances for the individualcomponents of the pumping mechanism significantly increase themanufacturing and service cost of the infusion system. Other infusionsystems and methods utilize varying ways of attempting to monitor theamount of the medication being delivered to the patient with one or moreadditional issues.

An infusion system and method is needed to reduce one or more issuesassociated with one or more of the current infusion systems and methods.

SUMMARY OF THE INVENTION

In one embodiment of the disclosure, an infusion system forautomatically detecting and adjusting a volumetric flow rate deliveredby an infusion pump is disclosed. The infusion system includes aninfusion pump, a flow path, at least one upstream acoustic sensor, atleast one downstream acoustic sensor, at least one processor, and atleast one memory. The infusion pump is configured to pump infusionfluid. The infusion fluid is configured to be delivered by the infusionpump along the flow path. The upstream acoustic sensor is located at anupstream location of the flow path. The downstream acoustic sensor islocated at a downstream location of the flow path. The downstreamacoustic sensor is configured to detect an upstream acoustic signalemitted by the upstream acoustic sensor. The upstream acoustic sensor isconfigured to detect a downstream acoustic signal emitted by thedownstream acoustic sensor. The processor is in electronic communicationwith the infusion pump, the upstream acoustic sensor, and the downstreamacoustic sensor. The memory is in electronic communication with theprocessor. The memory includes programming code for execution by theprocessor. The programming code is configured to determine a volumetricflow rate of the infusion fluid along the flow path based on theupstream acoustic signal detected by the downstream acoustic sensor andon the downstream acoustic signal detected by the upstream acousticsensor. The programming code is configured to determine the volumetricflow rate of the infusion fluid along the flow path based on a firstphase delay of the upstream acoustic signal between the upstreamacoustic sensor and the downstream acoustic sensor, and/or on a secondphase delay of the downstream acoustic signal between the downstreamacoustic sensor and the upstream acoustic sensor. The programming codeis further configured to automatically adjust the infusion pump based onthe determined volumetric flow rate, to achieve a desired volumetricflow rate of the infusion fluid along the flow path.

In another embodiment of the disclosure, a method for automaticallydetecting and adjusting a volumetric flow rate delivered by an infusionpump is disclosed. In one step, infusion fluid is delivered with aninfusion pump along a flow path. In another step, an upstream acousticsignal emitted by at least one upstream acoustic sensor, located at anupstream location of the flow path, is detected with at least onedownstream acoustic sensor located at a downstream location of the flowpath. In an additional step, a downstream acoustic signal emitted by thedownstream acoustic sensor, located at the downstream location of theflow path, is detected with the upstream acoustic sensor located at theupstream location of the flow path. In another step, a volumetric flowrate of the infusion fluid along the flow path is determined, with atleast one processor, over each stroke of the infusion pump based on theupstream acoustic signal detected by the downstream acoustic sensor andon the downstream acoustic signal detected by the upstream acousticsensor. The processor determines the volumetric flow rate of theinfusion fluid along the flow path over each stroke of the infusion pumpby determining a first phase delay of the upstream acoustic signalbetween the upstream acoustic sensor and the downstream acoustic sensor,or by determining a second phase delay of the downstream acoustic signalbetween the downstream acoustic sensor and the upstream acoustic sensor.In still another step, the infusion pump is automatically adjusted, withthe processor, over each pumping cycle of the infusion pump based on thedetermined volumetric flow rate to achieve a desired volumetric flowrate of the infusion fluid along the flow path.

In still another embodiment of the disclosure, a non-transitory computerreadable medium is disclosed. The non-transitory computer readablemedium is configured to, using at least one processor, automaticallydetect and adjust a volumetric flow rate of infusion fluid delivered byan infusion pump. The non-transitory computer readable medium includesprogramming code to command the processor to determine, over each strokeof the infusion pump, the volumetric flow rate of the infusion fluiddelivered by the infusion pump along a flow path. The programming codeis configured to determine, over each stroke of the infusion pump, thevolumetric flow rate based on an upstream acoustic signal emitted by atleast one upstream acoustic sensor, located at an upstream location ofthe flow path, which is detected by at least one downstream acousticsensor located at a downstream location of the flow path. Theprogramming code is further configured to determine, over each stroke ofthe infusion pump, the volumetric flow rate based on a downstreamacoustic signal emitted by the downstream acoustic sensor and detectedby the upstream acoustic sensor. The programming code is configured toautomatically adjust the infusion pump over each pumping cycle of theinfusion pump, based on the determined volumetric flow rate, to achievea desired volumetric flow rate of the infusion fluid along the flowpath.

In certain embodiments, an infusion system can automatically control aninfusion pump. The infusion system can include an infusion pump that canpump infusion fluid along a flow path. The infusion system can alsoinclude a first acoustic sensor positioned at a first location along theflow path, the first acoustic sensor can detect a first acoustic signal.The infusion system can further include a second acoustic sensorpositioned at a second location downstream from the first acousticsensor along the flow path. The second acoustic sensor can detect asecond acoustic signal. The infusion system can also include acontroller that can determine a first volumetric flow rate of theinfusion fluid based on the detected first acoustic signal and thedetected second acoustic signal. The controller can also control theinfusion pump to pump infusion fluid at a second volumetric flow ratebased on the detected first volumetric flow rate.

The infusion system of the preceding paragraph can have anysub-combination of the following features: wherein the first acousticsignal originated from the second acoustic sensor and the secondacoustic signal originated from the first acoustic sensor; wherein thefirst acoustic sensor comprises a first transducer and the secondacoustic sensor comprises a second transducer; wherein the firstacoustic sensor comprises a first transmitter and a first receiver andthe second acoustic sensor comprises a second transmitter and a secondreceiver; wherein the first receiver and the second receiver eachcomprise at least one noise cancelling component; wherein the firstvolumetric flow rate of the infusion fluid is calculated over eachstroke of the infusion pump; wherein the first volumetric flow rate isdetermined based on a first phase delay associated the first acousticsignal; wherein the first volumetric flow rate is determined based on asecond phase delay associated the second acoustic signal; wherein thefirst volumetric flow rate is determined based on a length between thefirst location and the second location; wherein the first volumetricflow rate is determined based on a first time it takes the firstacoustic signal to travel between the second acoustic sensor and thefirst acoustic sensor; wherein the first volumetric flow rate isdetermined based on a first time it takes the second acoustic signal totravel between the first acoustic sensor and the second acoustic sensor.

In certain embodiments, a method of controlling an infusion pump caninclude detecting a first acoustic signal from a first acoustic sensorpositioned at a first location along the flow path. The method canfurther include detecting a second acoustic signal from a secondacoustic sensor positioned at a second location downstream from thefirst acoustic sensor along the flow path. The method can also includedetermining a first volumetric flow rate of the infusion fluid based onthe detected first acoustic signal and the detected second acousticsignal. Moreover, the method can include changing the first volumetricflow rate to a second volumetric flow rate based on the determined firstvolumetric flow rate.

The method of the preceding paragraph can have any sub-combination ofthe following features: wherein the first acoustic signal originatedfrom the second acoustic sensor and the second acoustic signaloriginated from the first acoustic sensor; wherein the first acousticsensor comprises a first transducer and the second acoustic sensorcomprises a second transducer; wherein the first acoustic sensorcomprises a first transmitter and a first receiver and the secondacoustic sensor comprises a second transmitter and a second receiver;wherein the first receiver and the second receiver each comprise atleast one noise cancelling component; wherein the first volumetric flowrate of the infusion fluid is calculated over each stroke of theinfusion pump; wherein the first volumetric flow rate is determinedbased on a first phase delay associated the first acoustic signal;wherein the first volumetric flow rate is determined based on a secondphase delay associated the second acoustic signal; wherein the firstvolumetric flow rate is determined based on a length between the firstlocation and the second location; wherein the first volumetric flow rateis determined based on a first time it takes the first acoustic signalto travel between the second acoustic sensor and the first acousticsensor; wherein the first volumetric flow rate is determined based on afirst time it takes the second acoustic signal to travel between thefirst acoustic sensor and the second acoustic sensor.

These and other features, aspects and advantages of the disclosure willbecome better understood with reference to the following drawings,description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a box diagram of an infusionsystem;

FIG. 1A illustrates one embodiment of a pictorial view of a front of aninfusion pump with a pump cassette or infusion set cassette insertedinto the infusion pump;

FIG. 2 illustrates one embodiment of a side-view of an infusion setcassette illustrating configuration and placement of ultrasonic acoustictransducers;

FIG. 2A illustrates another embodiment of a side view of an infusion setcassette showing configuration and placement of ultrasonic acoustictransducers;

FIGS. 2B-2D illustrate various embodiments of a partial cross-sectionalview of a flow path of an infusion system showing the configuration andplacement of ultrasonic acoustic transducers;

FIG. 3 illustrates one embodiment of a simplified circuit diagramshowing an acoustic flow sensing system;

FIG. 3A illustrates another embodiment of a simplified circuit diagramshowing an acoustic flow sensing system;

FIG. 3B illustrates still another embodiment of a simplified circuitdiagram showing an acoustic flow sensing system;

FIG. 4 illustrates one embodiment of a graph showing two acousticpressure function curves, with time plotted on the X-axis and pressureplotted on the Y-axis, and a phase delay (difference between thereceived signal and the emitted signal) between the pressure functioncurves;

FIG. 5 illustrates one embodiment of a set of graphs in which twodifferent frequencies are transmitted, received, and processed by twodifferent transducers respectively;

FIG. 6 illustrates one embodiment of a flowchart showing a method ofautomatically detecting and adjusting a volumetric flow rate deliveredby an infusion pump;

FIG. 6A illustrates another embodiment of a flowchart showing a methodof automatically detecting and adjusting a volumetric flow ratedelivered by an infusion pump; and

FIG. 7 illustrates one embodiment of a graph, with time plotted on theX-axis and flow velocity plotted on the Y-axis, showing a flow profilewhen pumping is done by intermittent movement of a pumping mechanismcreating a periodic flow profile.

DETAILED DESCRIPTION

The following detailed disclosure describes one or more modes ofcarrying out the invention. The disclosure is not to be taken in alimiting sense, but is made merely for the purpose of illustrating thegeneral principles of the disclosure, since the scope of the disclosureis best defined by the appended claims. It is noted that the figures arepurely for illustrative purposes and are not to scale. It is furthernoted that any portions of the embodiments of the below disclosure maybe, in varying embodiments, combined in part or in full, one or morecomponents may be added, or one or more components may be removed.

FIG. 1 illustrates an embodiment of a box diagram of an infusion system10. The infusion system 10 can include an infusion pump or infuser 11and an infusion set 13 that is inserted in, and is acted upon by theinfusion pump 11. The infusion set 13 can include, among other elements,an inlet tube 4, an outlet tube 6 and a cassette 12. The infusion system10 can also include an infusion pump 11 with an infusion pumpingmechanism 15, a pump cassette 12, an infusion set 13 that has aninternal flow path 14, at least one upstream acoustic sensor 16, atleast one downstream acoustic sensor 18, at least one hardware processor20, at least one memory (also referred to herein as a non-transitorycomputer readable medium) 22, programming code 23, a proximalair-in-line sensor 24, a proximal pressure sensor 25, a distal pressuresensor 26, and a distal air-in-line air sensor 28. Signals from theinfusion pumping mechanism 15 and the sensors 16, 18, 24, 25, 26, 28 areacquired, conditioned if necessary, and sent to the hardware processor20 by signal acquisition electronics 27 to monitor proper operation offluid delivery. The hardware processor 20 can be programmed to executeprogramming code 23 or various algorithms stored in the memory 22 andcan control operation of the pumping mechanism 15 through the drivingelectronics. The programming code or instructions can be implemented inC, C++, JAVA, or any other suitable programming languages. In someembodiments, some or all of the portions of the programmed instructionscan be implemented in application specific circuitry 928 such as ASICsand FPGAs.

The infusion system 10 is configured to automatically detect and adjusta volumetric flow rate of infusion fluid 30 delivered by the infusionpump 11 along the flow path 14. In other embodiments, the infusionsystem 10 may include varying components varying in number, size, type,orientation, configuration, location, or function. For instance, inanother embodiment the infusion system 10 may not utilize a pumpcassette 12 (for example, see FIG. 2B and the description below).

As shown collectively in FIGS. 1 and 1A, the infusion pump 11 isoperatively coupled to the pump cassette 12. In other words, thecassette 12 is inserted in the infusion pump 11. The infusion pump 11 isconfigured to operate on the cassette 12 to pump the infusion fluid 30from a source or reservoir 2, which can be a bag, vial or othercontainer, through the inlet tube 4, at least one internal passageway ofthe cassette 12, and through the outlet tube 6 along the flow path 14,which may lead to a patient 8. In other embodiments, the flow path 14may be a flow path outside the pump cassette 12 or the pump cassette 12may not be present at all and the flow path 14 may be any flow path overwhich the infusion fluid 30 flows. The upstream acoustic sensor 16 iscoupled with the pump cassette 12 and located at an upstream location 14a of the flow path 14 at or integrated with the proximal pressure sensor25 which is coupled with the pump cassette 12. In other embodiments, theupstream acoustic sensor 16 may be located at or integrated with theproximal air-inline sensor 24 or located or integrated with varyingcomponents of the infusion system 10. The upstream acoustic sensor 16may include one or more ultrasonic sensors or other types of acousticsensor. Upstream and downstream are relative terms used herein toindicate the position of the sensors along the flow path. In anembodiment, the upstream sensor encounters the flow of fluid from thereservoir 2 before the downstream sensor.

In an embodiment, the downstream acoustic sensor 18 is coupled with thepump cassette 12 and located at a downstream location 14 b of the flowpath 14 at or integrated with the distal air-in-line sensor 28 which iscoupled with the pump cassette 12. In other embodiments, the downstreamacoustic sensor 18 may be located at or integrated with the distalpressure sensor 26 or located or integrated with varying components ofthe infusion system 10.

The downstream acoustic sensor 18 may include one or more ultrasonicsensors or other types of acoustic sensors. In an embodiment, thedownstream acoustic sensor 18 is configured to detect an upstreamacoustic signal emitted by the upstream acoustic sensor 16. The upstreamacoustic sensor 16 can also be configured to detect a downstreamacoustic signal emitted by the downstream acoustic sensor 18. In oneembodiment, the upstream acoustic sensor 16 and the downstream acousticsensor 18 may take turns, synchronized with the pumping mechanism of theinfusion pump 11, transmitting their respective upstream acoustic signaland downstream acoustic signal. The hardware processor 20 can calculatethe flow rate of the infusion fluid by integrating the phase delaymeasurement between the upstream and downstream signals over eachperiodic pumping interval. The pumping mechanism 15 operates in aperiodic manner, the flow measurement is obtained by the sensors 16 and18, and the flow is calculated by integration of the phase delaymeasurement over each individual periodic pumping interval as seen inFIG. 7. The flow measurement obtained by the sensors 16 and 18 can besynchronized with the period interval of the pumping mechanism 15 by thehardware processor 20 which determines the phase delay between theupstream and downstream signals over each stroke of the pumpingmechanism 15 (shown in FIG. 1) and uses the phase delay to determine thevolumetric flow rate of the infusion fluid over each stroke of thepumping mechanism 15. Moreover, the hardware processor 20 (shown inFIG. 1) is configured to make flow rate adjustments to the infusionfluid over each pumping cycle based on the determined flow rate overeach stroke of the pumping mechanism 15. Furthermore, the hardwareprocessor 20 (shown in FIG. 1) may average the determined flow ratesover a multitude of pump cycles and adjust the flow rate of the infusionfluid accordingly. In such manner, rapid update rate fluid deliverypumping correction can be achieved utilizing periodic sampling over thepumping period.

It is noted that the movement of infusion fluid into an IV line ismodulated by numerous items. The items that modulate the fluid flow arecomplex including but not limited to plunger movement, pump valveoperation, bag height, and patient relation to the pump chamber. Many ofthe dynamic changes are periodic in nature as depicted in FIG. 7. Thisperiodicity can be utilized to create a more rapid update rate foraverage flow. To have a reading of average flow by conventional means itmay require averaging the readings over several periodic periods.However, by gating the averaging by the periodic period the average canbe known in one periodic period. This can allow the control of fluiddelivery to be corrected much more quickly. In some embodiments, this ismuch more accurate for determining the flow rate than conventionalmethods. In such manner, the hardware processor of the infusion systemcan calculate the phase delay over each stroke to determine the flowrate over each stroke and by subsequently adjusting the flow rate overeach pumping cycle based on the determined flow rate, the infusionsystem has superior flow rate accuracy over conventional systems andmethods. This allows for the use of the infusion system over a muchlonger period of time as diaphragm deterioration and other deteriorationof the components of the infusion system may be accounted for inreal-time during each pumping cycle of the pumping mechanism byadjusting the flow rate of the infusion fluid accordingly.

In another embodiment, the upstream acoustic sensor 16 and thedownstream acoustic sensor 18 may continuously transmit their respectiveupstream acoustic signal and downstream acoustic signal or themeasurements may occur over a given number of periodic intervals. Oneskilled in the art will recognize that the terms “upstream” and“downstream”, as used herein, are terms that describe the location ofone component of the system with respect to one or more other componentsof the system. The flow path 14 can be thought of as a river where fluidis normally flowing from the source 2 to the patient 8. In anembodiment, the upstream acoustic sensor 16 is located between thepumping mechanism 15 and the reservoir 2 or upstream of the pumpingmechanism 15, and the downstream acoustic sensor 18 is located betweenthe pumping mechanism 15 and the patient 8 or downstream of the pumpingmechanism 15. The upstream acoustic sensor 16 is located upstream alongthe normal flow path 14 from the downstream acoustic sensor 18. Oneskilled in the art will also appreciate that the upstream and downstreamacoustic sensors 16 and 18 could be referred to as proximal and distalacoustic sensors respectively.

FIGS. 2 and 2A illustrate two different possible configurations andplacements of acoustic sensors 16 and 18 against or adjacent to acassette 12 as shown relative to the inlet tube 4 and the outlet tube 6.The acoustic sensors 16 and 18 are non-invasive ultrasonic transducers16T and 18T. The transducers 16T and 18T have double function ofemitters and receivers. The transducers 16T and 18T contact the cassette12 by means of coupling elements. The coupling elements 16C and 18C aremade of a compliant material and ensure good acoustic contact. In oneembodiment, the transducers 16T and 18T with their coupling elements 16Cand 18C are part of the pump 11 (shown in FIG. 1).

FIG. 2B illustrates one embodiment of a cross-section view through aportion of an infusion system 10 in which the disclosure could beimplemented showing the flow path 14, the one upstream acoustic sensor16, and the one downstream acoustic sensor 18. The upstream acousticsensor 16 includes a first transducer 16T that includes a transmitter16E and a first receiver 16R which are shown in greater detail withtheir accompanying electronics in FIG. 3. The first receiver 16Rincludes a noise cancelling component such as a noise cancellingmicrophone 16M. Similarly, the downstream acoustic sensor 18 includes asecond transducer 18T that includes a transmitter 18E and a secondreceiver 18R which are shown in greater detail with their accompanyingelectronics in FIG. 3. The second receiver 18R can also include a noisecancelling component such as a noise cancelling microphone 18M. Inadditional embodiments, the upstream acoustic sensor 16 and thedownstream acoustic sensor 18 may further vary.

FIG. 2C illustrates another embodiment of a cross-section view through aportion of an infusion system 10 in which the disclosure could beimplemented showing the flow path 14, the upstream acoustic sensor 16,and the downstream acoustic sensor 18. The upstream acoustic sensor 16can include a first transducer 16T, and the downstream acoustic sensor18 includes a second transducer 18T. The first transducer 16T and thesecond transducer 18T may each include or be connected to a noisecancelling component such as noise cancelling microphones 16M and 18M.In additional embodiments, the upstream acoustic sensor 16 and thedownstream acoustic sensor 18 may further vary.

In another embodiment shown in FIG. 2A, the existing cassette 12 isenhanced by the addition of a straight rigid tube 12T with a preciseinternal bore. The tube 12T can be part of the cassette 12 as anextension of its outlet port. The transducers 16T and 18T make contactwith the tube 12T or are coupled to the tube 12T by the couplingelements 16C and 18C.

In another embodiment shown in FIG. 2D, the infusion system 10 may ormay not include a cassette, but includes in the flow path 14 a straightrigid tube 12T that has a precisely dimensioned internal bore. If thesystem 10 includes a cassette (shown in FIG. 1 as cassette 12), therigid tube 12T is located downstream of the cassette and is connected toor integrated with an outlet tube (shown in FIG. 1 as outlet tube 6). Ifthe system does not include a cassette, the tube 12T can be locateddownstream of whatever pumping mechanism (shown in FIG. 1 as pumpingmechanism 15) exists. In the case of gravity flow where no pumpingmechanism exists other than gravity, the tube 12T can be located betweenthe source (shown in FIG. 1 as source 2) and the patient (shown in FIG.1 as patient 8), downstream of a conventional clamp or valve (not shown)for controlling the flow of the infusion fluid 30. The infusion fluid 30enters the tube 12T through an inlet and flows to an outlet. Theupstream transducer 16T is coupled to the tube 12T adjacent to the inletby a coupling element 16C. The downstream transducer 18T is coupled tothe tube 12T adjacent to the outlet by a coupling element 18C.

Taking as an example the embodiment in FIG. 2D, FIG. 3 shows oneembodiment of the flow sensor circuits which may be utilized to monitorthe flow rate of the infusion fluid 30. In this case, the transducers16T, 18T can be transducers or can each include separate emitters ortransmitters 16E, 18E and receivers 16R, 18R. The transmitter andreceiver function can be accomplished by the same transducer or byseparate transducers performing each a single function. The transmitters16E and 18E can emit ultrasonic signals and the receivers 16R and 18Rreceive the ultrasonic signals from the transmitters 18E and 16E. Thereceivers 16R and 18R can include noise cancelling components such asnoise cancelling microphones 16M and 18M. The microcontroller 302 (alsoreferred to as a hardware processor herein which could include one ormore hardware processors) commands a frequency generator 304 to generatea voltage signal with the programmed frequency f A driver 306 amplifiesthe signal and sends it to the emitter 16E of one of the transducers16T. The emitter 16E generates an ultrasonic signal S that propagatesthrough the fluid 30 and is detected by the receiver 18R at the otherend of the tube, which generates a voltage signal proportional to thereceived ultrasonic signal R. The emitted signal S and the receivedsignal R are fed to a phase comparator 308 that generates a signalproportional to the phase difference between the two signals. A signalconditioning stage 310 amplifies and filters the signal and sends it toan analog to digital converter 312 that converts it to a digital phasesignal received by the microcontroller 302. The microcontroller 302controls the switches 314A, 314B, 314C, 314D that select the propagationdirection of the ultrasonic signal. In this embodiment the signal S isemitted alternatively with and against the flow direction. When thesignal S is to be emitted with the direction of fluid flow, the normallyclosed switches 314A and 314B are closed and the normally open switches314C and 314D are open; and when the signal S is to be emitted in theopposite direction, against the direction of fluid flow, themicrocontroller 302 opens switches 314A and 314B and closes switches314C and 314D. The transmitter and receiver transducers can bepiezoelectric, electromagnetic, or microelectromechanical systems (MEMS)based in construction.

Taking as an example the embodiment of FIG. 20, FIG. 3A shows anotherembodiment of the flow sensor circuits which may be utilized to monitorthe flow rate of the infusion fluid 30. In this case the transducers 16Tand 18T still contain separate emitters 16E and 18E and receivers 16Rand 18R, but the transducers 16T and 18T are operated continuously. Inother words, the case of simultaneous transmission with separatetransmitter and receiver transducers is illustrated. There are twoseparate channels, one for the acoustic signal propagating against theflow and one for the acoustic signal propagating with the flow. Theprogrammed frequencies f₁ and f₂ of the signals S1 and S2 in the twochannels are different, so they can be separated by the phasecomparators 308A and 3088. The microcontroller 302 commands a frequencygenerator 304A to generate a voltage signal with the programmedfrequency f₁. A driver 306A amplifies the signal S1 and sends it to theemitter 16E of one of the transducers 16T. The emitter 16E generates anultrasonic signal that propagates through the fluid 30 and is detectedby the receiver 18R at the other end of the tube, which generates avoltage signal proportional to the received ultrasonic signal R 1. Theemitted signal S1 and the received signal R1 are fed to a phasecomparator 308A that generates a signal proportional to the phasedifference between the two signals. A signal conditioning stage 31 OAamplifies and filters the signal and sends it to an analog to digitalconverter 312A that converts it to a digital phase signal received bythe microcontroller 302. The microcontroller 302 further commands afrequency generator 3048 to generate a voltage signal with theprogrammed frequency f₂. A driver 3068 amplifies the signal S2 and sendsit to the emitter 18E of one of the transducers 18T. The emitter 18Egenerates an ultrasonic signal that propagates through the fluid 30 andis detected by the receiver 16R at the other end of the tube, whichgenerates a voltage signal proportional to the received ultrasonicsignal R2. The emitted signal S2 and the received signal R2 are fed to aphase comparator 3088 that generates a signal proportional to the phasedifference between the two signals. A signal conditioning stage 31 OBamplifies and filters the signal and sends it to an analog to digitalconverter 3128 that converts it to a digital phase signal received bythe microcontroller 302. The transmitter and receiver transducers can bepiezoelectric, electromagnetic, or microelectromechanical systems (MEMS)based in construction.

Again taking as an example the embodiment of FIG. 2B, FIG. 3B showsanother embodiment of the flow sensor circuits which may be utilized tomonitor the flow rate of the infusion fluid 30. In this case, thetransducers 16T and 18T perform both functions of emitting and receivingthe ultrasonic signals. The transducers 16T and 18T transmitsimultaneously and are operated continuously. There are still twoseparate channels. The frequencies f1, f2 of the signals S1 and S2 inthe two channels are different, so they can be separated by the phasecomparators 308A and 308B. The voltage at the terminals of each of thetransducers 16T and 18T is the sum of the emitted signals S1 and S2voltages from the drivers 306A and 306B and the voltages generated bythe transducers 16T and 18T, which is proportional to the receivedsignals R2 and R1. Difference amplifiers 316A and 316B subtract theemitted signals S1 or S2 from this sum, outputting the received signalsR2 or R1 respectively. The microcontroller 302 (also referred to as aprocessor herein which could include one or more processors) commandsfrequency generator 304A to generate a voltage signal with theprogrammed frequency f₁. A driver 306A amplifies the signal S1 and sendsit to the transducer 16T. The transducer 16T generates an ultrasonicsignal that propagates through the fluid 30 and is detected by thetransducer 18T at the other end of the tube, which generates a voltagesignal of the sum of the received ultrasonic signal R1 and the signal S2transmitted by the transducer 18T. Difference amplifier 316A subtractsthe emitted signal S2 from this sum, outputting the received signal R1.The emitted signal S1 and the received signal R1 are fed to a phasecomparator 308A that generates a signal proportional to the phasedifference between the two signals. A signal conditioning stage 310Aamplifies and filters the signal and sends it to an analog to digitalconverter 312A that converts it to a digital phase signal received bythe microcontroller 302. The microcontroller 302 further commandsfrequency generator 304B to generate a voltage signal with theprogrammed frequency f₂. A driver 306B amplifies the signal S2 and sendsit to the transducer 18T. The transducer 18T generates an ultrasonicsignal that propagates through the fluid 30 and is detected by thetransducer 16T at the other end of the tube, which generates a voltagesignal of the sum of the received ultrasonic signal R2 and the signal S1transmitted by the transducer 16T. Difference amplifier 316B subtractsthe emitted signal S1 from this sum, outputting the received signal R2.The emitted signal S2 and the received signal R2 are fed to a phasecomparator 308B that generates a signal proportional to the phasedifference between the two signals. A signal conditioning stage 310Bamplifies and filters the signal and sends it to an analog to digitalconverter 312B that converts it to a digital phase signal received bythe microcontroller 302. The transmitter and receiver transducers can bepiezoelectric, electromagnetic, or microelectromechanical systems (MEMS)based in construction.

As shown in FIG. 1 (and as further detailed in other embodiments hereinusing the same or different reference numbers), the hardware processor20 is in electronic communication with the infusion pump 11, theupstream acoustic sensor 16, the downstream acoustic sensor 18, the onememory 22, the proximal air-in-line sensor 24, the proximal pressuresensor 25, the distal pressure sensor 26, and the distal air-in-line airsensor 28. The memory 22 contains the programming code 23 which isconfigured to be executed by the processor 20. The programming code 23is configured to determine the volumetric flow rate of the infusionfluid 30 along the flow path 14 based on the upstream acoustic signaldetected by the downstream acoustic sensor 18 and on the downstreamacoustic signal detected by the upstream acoustic sensor 16, and toautomatically adjust the infusion pump 11, based on the determinedvolumetric flow rate, to achieve a desired volumetric flow rate of theinfusion fluid 30 along the flow path 14.

In the embodiments of FIGS. 3, 3A and 3B, the hardware processor 20executing the programming code 23 (shown in FIG. 1) can determine thevolumetric flow rate of the infusion fluid 30 along the flow path 14based on a first phase delay of the upstream acoustic signal between theone upstream acoustic sensor 16 and the downstream acoustic sensor 18,or on a second phase delay of the downstream acoustic signal between thedownstream acoustic sensor 18 and the upstream acoustic sensor 16.

In the embodiment of FIG. 1, the hardware processor 20 executing theprogramming code 23 is configured to determine the volumetric flow rateof the infusion fluid 30 along the flow path 14 by using the algorithmQ=V*A. In the algorithm, Q includes the volumetric flow rate, V includesa velocity of the infusion fluid 30 generated by the infusion pump 11,and A includes a cross-sectional area of the flow path 14. Moreover,V=(L/2)*(1/t₁−1/t₂), wherein L includes a length between the upstreamlocation 14 a and the downstream location 14 b, t₁ includes a first timeit takes the upstream acoustic signal to travel from the one upstreamacoustic sensor 16 to the downstream acoustic sensor 18, and t₂ includesa second time it takes the downstream acoustic signal to travel from thedownstream acoustic sensor 18 to the one upstream acoustic sensor 16. Inother words, t₁-t₂ can be thought of as the transit time of the signalor delta t. The distance between the sensors divided by delta t is thespeed of the flow stream. The speed times the area of flow path equalsthe volumetric flow rate.

FIG. 4 illustrates a graph 32 of one embodiment of two acoustic pressurefunction curves 34 and 36 plotting time on the X-axis and pressure onthe Y-axis to show the phase delay between the pressure function curves34 and 36. Acoustic pressure function curve 34 includes the pressurewave at the origin of the upstream acoustic sensor 16 or 16T of FIG. 28.Acoustic pressure function curve 36 includes the pressure wave atdistance x from the origin of the downstream acoustic sensor 18 or 18Tof FIG. 2B. There is a delay time t_(x) between the two acousticpressure function curves 34 and 36. The two acoustic pressure functioncurves 34 and 36 represent periodic variations in time and space of thepressure in the liquid. It can be assumed that the pressure at thesource is a simple sinusoidal function represented by P(0,t)=P₀sin(2*π*f*t), where P₀ includes pressure amplitude, f includes frequencyof the sound wave, and t includes time.

At the distance x, the wave 36 is delayed by the time t_(x) or, toexpress it in another way, the argument of the sine function is changedby the phase angle φ so that

P(x,t)=P₀ sin[2*π*f*(t−t_(x))]=P₀ sin(2*π*f*t+φ). Using an electroniccircuit called a phase discriminator, which is known in the art, tomeasure the phase angle between the two waves, the delay time betweenthe wave 34 emitted and the wave 36 received at a certain distance maybe calculated as being t_(x)=−φI2*π*f. In order to reduce the size ofthe measurement apparatus, shorter time measurements may be required dueto the short distance between the transmitter and receiver. Theseshorter time measurements over the shorter distances can be accomplishedthrough the use of the phase discriminator. In order to increase theresolution of the fluid flow without restricting the area of the flowchannel a differential measurement is used. This measurement is done bydetermining the phase delay between the transmitter and receiver of acontinuous signal. To convert this phase angle measurement to fluidspeed it is necessary to take the period of the repetitive signal timesthe angle, according to the t_(x) equation shown above.

For example, in the case of a short distance between the transmitter andreceiver (less than a full cycle), given a predetermined/designedoscillator frequency f=5 MHz and a measured phase delay angle of 12degrees, the method might determine:

Calculated time delay t _(x) =−φI2*π*f

tx=−12 deg./(2π5 MHz)=42 nsecs

Thus, this method allows a small time delay to be measured. Utilizationof signal phase shift allows measurement of a very small time delay.Advantageously, this can translate into accurate measurements over veryshort distances too. This is accomplished by utilizing a carrier signalphase shift between the signal emitted by the transmitter source to thesignal at the receiver. The process described herein can be furtherillustrated in FIGS. 4 and 5.

The determined time delay can be used to determine the velocity V of thefluid, which in turn can be used to determine the volumetric flow rateQ. An illustration of velocity computation follows with a hypotheticalnumerical example where: V=(L)*(1/t₁−1/t₂); tx=(1/t₁−1/t₂); andL=distance between transmitter and receiver.

In a phase approach, over longer distances than the example above,several full cycles may exist between the transmitter and the receiverdue to the distance or length L between them. For purposes ofillustration below we will utilize 50 full cycles, plus a partial cyclethat is measured as a phase delay. Assuming L is predetermined ordesigned to equal 0.005 m, the frequency of the carrier is 10 kHz, andϕ=143 deg (measured):

Given the above t_(x) will be:

(converting the angle to time)

tx(143 deg+50*360 deg)/2*π*10kHZ=835 μS

(then converting the time to velocity)

$V = {\frac{{.005}\mspace{14mu} m}{tx} = {5.98\mspace{14mu} m\text{/}s}}$

Area, A, is the cross sectional area of the flow path (in this examplethe flow path is a tube or tubing with an inside diameter of 0.0003meters)

${Area} = {{\left( \frac{{.0003}\mspace{14mu} m}{2} \right)^{2}*\pi} = {0.071\mspace{14mu} {mm}^{2}}}$

This gives the volumetric flow rate Q=V*A

Q=V*Area=1523 ml/hr

In the above equation, Q includes the volumetric flow rate, V includes avelocity of the infusion fluid 30 generated by the infusion pump 11, andA includes a cross-sectional area of the flow path 14.

So to review and summarize, the overall time propagation of the soundwaves 34 and 36 will be affected by the flow of the fluid through thetubing and/or channel. There will be a difference in the delays sincethe propagation occurs faster downstream than upstream so that t₁=L/C+V,and t₂=L/C−V, wherein t₁ includes the time of sound propagationdownstream, t₂ includes the time of sound propagation upstream, Lincludes a length of sound propagation path in the fluid channel, Cincludes sound velocity in the fluid, and v includes a velocity of fluidgenerated by the infuser. If the times are known, the following equationcan be used 1/t₁−1/t₂=(2*V)/L. From this equation, the followingequation can be obtained V=(L/2)*(1/t₁−1/t₂). If the cross section areaof the flow path A is known, the volumetric flow rate Q can becalculated using the equation Q=V*A. In the embodiment of FIG. 1, thehardware processor 20 executing the programming code 23 can determinethe volumetric flow rate of the infusion fluid 30 along the flow path 14based on the phase delay by using the equations above.

FIG. 5 illustrates one embodiment of a set of graphs in which twodifferent frequencies are transmitted, received, and processed by twodifferent transducers respectively. The graphs depict the varying phasedelays of the differing frequencies.

FIG. 6 illustrates a flowchart of one embodiment of a method 400 ofautomatically detecting and adjusting a volumetric flow rate deliveredby an infusion pump. FIG. 6 can also be thought of as a block diagram ofclosed loop control using flow sensing transduces. The method 400 mayutilize any of the infusion systems disclosed herein. In otherembodiments, the method 400 may utilize varying infusion systems. Themethod can start at node 402. In step 404, the infusion parametersincluding desired fluid flow rate, duration and dose are programmed bythe user. Initially prompted by a start command from a user, in step406, the hardware processor coordinates the pump in pumping fluidaccording to the programmed parameters. In step 408, the fluid flow ismeasured as described above and further explained with reference to FIG.6A below. In step 410, the measured value is converted to engineeringunits (cm/s, m/s, etc.) expressing the measured actual flow rate of thefluid. Scaling based on the physical dimensions of the tube or flowchannel and time offsets may be utilized. In step 412, the actualdelivered volume is calculated based upon the measured flow rate and instep 414, the actual delivered volume is compared to the programmed ordesired volume based upon the programmed delivery flow rate. If theactual flow rate is equal to the desired flow rate and thus thedelivered volume is correct, then the method proceeds to step 416A andthe pump can continue as is or be stopped if the full programmed volumeto be infused has been reached. If the actual flow deviates or is notequal to the desired flow and thus the delivered volume is incorrect,the method proceeds to step 4168 where an adjustment to the pumpingparameters such as the programmed or desire flow rate is determined. Inoptional step 418 the adjustment or the new program parameter can beevaluated for acceptability by a processor against a limit or range oflimits in a memory. The limits can be hard coded into the pump orincluded in a user-customizable drug library that can be downloaded tothe processor or memory of the pump over a network. If the adjustment oradjusted program parameter is outside the acceptable range or exceeds anacceptable limit, then an optional alarm is generated in step 420. Thealarm can be communicated visually, audibly, by other perceptible meansor merely relayed electronically to a remote device. If the adjustmentor adjusted program parameter such as a new desired flow rate is withinthe acceptable range or limit, the method moves back to step 406 and themethod continues with the pump processor being automatically programmedto pump the fluid according to the newly adjusted program parameter suchas a new flow rate. In other embodiments, one or more steps of themethod 400 may be changed in substance or order, one or more steps ofthe method 400 may not be followed, or one or more additional steps maybe added.

With reference to FIG. 6A, in one embodiment the flow measurement step408 and others from FIG. 6 are disclosed in greater detail as the stepsof a flow measurement and automatic adjustment process 40. In step 42,infusion fluid is delivered with an infusion pump along a flow path of apump cassette. In step 44, an upstream acoustic signal emitted by theupstream acoustic sensor, coupled with the pump cassette and located atan upstream location of the flow path, is detected with the downstreamacoustic sensor coupled with the pump cassette and located at adownstream location of the flow path. The upstream acoustic sensor mayinclude at least one ultrasonic upstream acoustic sensor. In otherembodiments, the upstream acoustic sensor may vary. In one embodiment,step 44 may include detecting the upstream acoustic signal emitted bythe upstream acoustic sensor by receiving the upstream acoustic signalwith a first noise cancelling component such as a first noise cancellingmicrophone.

In step 46, a downstream acoustic signal emitted by the downstreamacoustic sensor, coupled with the pump cassette and located at thedownstream location of the flow path, is detected with the upstreamacoustic sensor coupled with the pump cassette and located at theupstream location of the flow path. The downstream acoustic sensor mayinclude one or more ultrasonic upstream acoustic sensor. In otherembodiments, the downstream acoustic sensor may vary. In one embodiment,step 46 may include detecting the downstream acoustic signal emitted bythe downstream acoustic sensor by receiving the downstream acousticsignal with a second noise cancelling component such as a second noisecancelling microphone. In step 48, a volumetric flow rate is determined,with the hardware processor, of the infusion fluid along the flow pathbased on the upstream acoustic signal detected by the downstreamacoustic sensor and the downstream acoustic signal detected by theupstream acoustic sensor.

In one embodiment, step 48 may include determining, with the hardwareprocessor, the volumetric flow rate of the infusion fluid along the flowpath by determining a first phase delay of the upstream acoustic signalbetween the upstream acoustic sensor and the downstream acoustic sensor,or by determining a second phase delay of the downstream acoustic signalbetween the downstream acoustic sensor and the upstream acoustic sensor.This may be done using an algorithm executed by the hardware processor20.

In another embodiment, step 48 may include determining, with theprocessor, the volumetric flow rate of the infusion fluid along the flowpath by using the algorithm Q=V*A, wherein Q includes the volumetricflow rate, V includes a velocity of the infusion fluid generated by theinfusion pump, A includes a cross-section area of the flow path, andV=(L/2)*(1/t₁−1/t₂), wherein L includes a length between the upstreamlocation and the downstream location, t₁ includes a first time it takesthe upstream acoustic signal to travel from the upstream acoustic sensorto the downstream acoustic sensor, and t₂ includes a second time ittakes the downstream acoustic signal to travel from the downstreamacoustic sensor to the upstream acoustic sensor.

In step 50, the infusion pump is automatically adjusted, with thehardware processor, based on the determined volumetric flow rate toachieve a desired volumetric flow rate of the infusion fluid along theflow path. In other embodiments, one or more steps of the method 40 maybe changed in substance or order, one or more steps of the method 40 maynot be followed, or one or more additional steps may be added. It isnoted that the method 40 may utilize any of the system or methodembodiments disclosed herein. One or more embodiments of the disclosureallows for improved accuracy of determining how much infusion fluid isbeing delivered to the patient while decreasing manufacturing cost ofthe infusion system. It should be understood, of course, that theforegoing relates to exemplary embodiments of the disclosure and thatmodifications may be made without departing from the scope of thedisclosure as set forth in the following claims.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise”, “comprising”, and thelike, are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense, that is to say, in the sense of“including, but not limited to”.

Reference to any prior art in this specification is not, and should notbe taken as, an acknowledgement or any form of suggestion that thatprior art forms part of the common general knowledge in the field ofendeavour in any country in the world.

The disclosed apparatus and systems may also be said broadly to consistin the parts, elements and features referred to or indicated in thespecification of the application, individually or collectively, in anyor all combinations of two or more of said parts, elements or features.

Where, in the foregoing description reference has been made to integersor components having known equivalents thereof, those integers areherein incorporated as if individually set forth.

Depending on the embodiment, certain acts, events, or functions of anyof the algorithms, methods, or processes described herein can beperformed in a different sequence, can be added, merged, or left outaltogether (e.g., not all described acts or events are necessary for thepractice of the algorithms). Moreover, in certain embodiments, acts orevents can be performed concurrently, e.g., through multi-threadedprocessing, interrupt processing, or multiple processors or processorcores or on other parallel architectures, rather than sequentially.

It should be noted that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the disclosed apparatusand systems and without diminishing its attendant advantages. Forinstance, various components may be repositioned as desired. It istherefore intended that such changes and modifications be includedwithin the scope of the disclosed apparatus and systems. Moreover, notall of the features, aspects and advantages are necessarily required topractice the disclosed apparatus and systems. Accordingly, the scope ofthe disclosed apparatus and systems is intended to be defined only bythe claims that follow.

1. An infusion system configured to automatically control an infusionpump, the infusion system comprising: an infusion pump configured topump an infusion fluid along a flow path; a first acoustic sensorpositioned at a first location along the flow path, the first acousticsensor configured to detect a first acoustic signal; a second acousticsensor positioned at a second location downstream from the firstacoustic sensor along the flow path, the second acoustic sensorconfigured to detect a second acoustic signal; and a controllerconfigured to: determine a first volumetric flow rate of the infusionfluid based on the detected first acoustic signal and the detectedsecond acoustic signal, and control the infusion pump to pump theinfusion fluid at a second volumetric flow rate based on the detectedfirst volumetric flow rate.
 2. The infusion system of claim 1, whereinthe first acoustic signal originated from the second acoustic sensor andthe second acoustic signal originated from the first acoustic sensor. 3.The infusion system of claim 1, wherein the first acoustic sensorcomprises a first transducer and the second acoustic sensor comprises asecond transducer.
 4. The infusion system as in claim 1, wherein thefirst acoustic sensor comprises a first transmitter and a first receiverand the second acoustic sensor comprises a second transmitter and asecond receiver.
 5. The infusion system of claim 4, wherein the firstreceiver and the second receiver each comprise at least one noisecancelling component.
 6. The infusion system of claim 1, wherein thefirst volumetric flow rate of the infusion fluid is calculated over eachstroke of the infusion pump.
 7. The infusion system of claim 1, whereinthe first volumetric flow rate is determined based on a first phasedelay associated the first acoustic signal.
 8. The infusion system as inclaim 1, wherein the first volumetric flow rate is determined based on asecond phase delay associated the second acoustic signal.
 9. Theinfusion system as claim 1, wherein the first volumetric flow rate isdetermined based on a length between the first location and the secondlocation.
 10. The infusion system as claim 1, wherein the firstvolumetric flow rate is determined based on a first time it takes thefirst acoustic signal to travel between the second acoustic sensor andthe first acoustic sensor.
 11. The infusion system of claim 1, whereinthe first volumetric flow rate is determined based on a first time ittakes the second acoustic signal to travel between the first acousticsensor and the second acoustic sensor.
 12. A method of controlling aninfusion pump configured to pump infusion fluid along a flow path, themethod comprising: detecting a first acoustic signal from a firstacoustic sensor positioned at a first location along the flow path;detecting a second acoustic signal from a second acoustic sensorpositioned at a second location downstream from the first acousticsensor along the flow path; determining a first volumetric flow rate ofthe infusion fluid based on the detected first acoustic signal and thedetected second acoustic signal; and changing the first volumetric flowrate to a second volumetric flow rate based on the determined firstvolumetric flow rate.
 13. The method of claim 12, wherein the firstacoustic signal originated from the second acoustic sensor and thesecond acoustic signal originated from the first acoustic sensor. 14.The method of claim 12, wherein the first acoustic sensor comprises afirst transducer and the second acoustic sensor comprises a secondtransducer.
 15. The method as in claim 12, wherein the first acousticsensor comprises a first transmitter and a first receiver and the secondacoustic sensor comprises a second transmitter and a second receiver.16.-37. (canceled)